The present invention relates to a single use camera with built-in electronic flash.
In the conventional single use camera with built-in electronic flash, in the stroboscopic photographing, there is a problem in which a main object in a distance of 2-3 m is a little overly exposed into a rather white image, and, on the other hand, its background is a little under-exposed into a rather dark image, resulting in unbalance as a total image.
Further, recently, in the single use camera, due to its increasing competition in the market, requirements for the unit are to design it to be more compact, and to manufacture it to be more inexpensive. Specifically, in the single use camera with built-in electronic flash, the influence of the electronic flash on the reduction of size or cost is extremely great.
As a type of electronic flash switch actuator, there is an automatic-return type which is turned ON when only operated by the operator, and which is returned to an OFF-state when the operator does not touch it, and which also opens a main switch in the electronic flash circuit, and a state holding type such as a slide type, seesaw type, or standing-up type, which holds the ON-state even when the operator stops touching it, and which maintains a main switch in the electronic flash circuit to be closed.
When the electronic flash switch actuator is the type of state holding type, there is an advantage that no charging operation is required for each continuous stroboscopic photographing, however, when the operator forgets to turn OFF the electronic flash switch actuator, and an ON state continues, the electronic flash charging operation is continued, resulting in useless consumption, and therefore, there is a possibility that stroboscopic photographing comes to be impossible before the entire exposures of a film roll are exposed.
For example, as an example of the single use camera with built-in electronic flash now in the market, an alkaline dry battery of 1.5 volts is used as its power source. When resistance of a step-up circuit of the electronic flash circuit is 220 xcexa9, the holding time of the dry battery voltage more than 1 v by which the electronic flash unit can be charged, is about 6 hours (refer to FIG. 14). Accordingly, when a night is over while the operator forgets turning OFF the electronic flash switch actuator, there is a case where, on the next day, the battery is exhausted up and no stroboscopic photographing can be done.
Further, in an electronic flash circuit of the conventional electronic flash unit, two switches are required one of which is a main switch to charge the electronic flash unit when it is used, and the other of which is a light emission stop switch to turn OFF a neon tube and to stop the light emission of the electronic flash unit even when the main capacitor is charged. Thereby, it results in cost-up, and further, there is a case where an electronic flash unit failure caused by these switches occurs.
Herein, the conventional electronic flash unit will be detailed below. The conventional electronic flash circuit is shown in FIG. 2.
In FIG. 2, BT is a battery consists of a SUM-3 type (or AA type) or SUM-4 type (or AAA type) dry battery, and when stroboscopic photographing is carried out, a main switch SW1 and a light emission stop switch SW2 are turned ON by operating an external operation member. Then, DC current is supplied from the battery BT to an oscillation transistor Q, oscillation transformer T1, and a resistor R1 through the main switch SW1, and an oscillation operation is carried out so that low DC voltage is converted into AC high voltage.
The AC high voltage outputted from the oscillation transformer T1 is rectified by a diode D, and charges the main capacitor C1. Further, a trigger capacitor C2 is charged through a resistor R2. When the voltage of the trigger capacitor C2 reaches a predetermined voltage value, the voltage is applied to a resistor R3 and a neon tube Ne, and the neon tube Ne starts discharging, that is, it is turned ON.
As described above, after the neon tube Ne is turned ON, when a release button, not shown, is pressed, a shutter blade is opened, and when the blade is fully opened, a trigger switch TSW is turned ON. When the trigger switch TSW is turned ON, electric charges, which are charged in the trigger capacitor C2, are discharged onto a primary winding T21 of a trigger coil T2, high voltage is generated in a secondary winding T22 and the voltage is applied to a trigger electrode G of a discharge tube Xe. As the result, ionized xenon atoms in the discharge tube Xe collide with electrons sprung out from a cathode and are excited, and thereby, the discharge tube Xe is lit.
Further, while the main capacitor C1 is charged and the neon tube Ne is lit, when the main switch SW1 is turned OFF by operating the external operation member, the oscillating operation is stopped. Further, the light emission stop switch SW2 is also simultaneously turned OFF, thereby, the neon tube Ne is turned OFF, and even when the release button is further pressed and the trigger switch TSW is turned ON, the trigger capacitor C2 does not discharge, thereby, the discharge tube Xe does not emit light.
Next, as an alternative means for cost reduction, it is also considered that, as an indicator lamp, an expensive neon tube is not used, but an inexpensive light emitting diode is used, and the description relating to this is disclosed in Japanese Patent Publication Open to Public Inspection No. 115796/1996. However, when the neon tube is not used but the light emitting diode is used, there is a problem that the trigger voltage outputted from the trigger transformer becomes too high. Further, when the light emitting diode is used as the indicator lamp, an amount of light emission or lighting timing can be adjusted using characteristics of the light emitting diode, however, in the structure stated above, in which the tertiary winding of the oscillating transformer is used also for a lighting circuit of the light emitting diode, there are disadvantages that the number of windings of the tertiary winding is set for the control of the oscillating transistor, therefore, when the number of windings of the tertiary winding is increased or decreased for, for example, the light amount adjustment of the light emitting diode, the discharging voltage is lowered, thereby, the charging characteristics are also changed like that, for example, a long period of time is necessary for charging.
In this connection, a detail of the conventional electronic flash circuit in which the light emitting diode is used as the indicator lamp, is shown in FIG. 25. An electronic flash circuit 301 is largely divided into a step-up circuit 302 to step up the power source such as a dry battery BT, and a flash light emitting circuit 303 to make the electronic flash light emitting tube Xe emit light. In the step-up circuit 302, an oscillating transformer TR1 and oscillating transistor Q, and further, a light emitting diode LED as an indicator lamp are provided, and in the flash light emitting circuit 303, an electronic flash light emitting tube Xe, a main capacitor MC, and a trigger switch TSW are provided.
The oscillating transformer TR1 in the step-up circuit 302 has a primary winding W1, a secondary winding W2, and a tertiary winding W3 as a feed back winding. The AC high voltage is generated in the secondary winding corresponding to a turns ratio of primary winding to secondary winding, and the tertiary winding W3 controls to stabilize the base potential voltage of the oscillating transistor Q, and the light emitting diode LED is connected to both ends of the tertiary winding W3 of the oscillating transformer TR1, and thus, a light emitting diode lighting circuit 304 (hereinafter, referred to as LED lighting circuit) is structured.
The high voltage generated by the oscillating transformer TR1 by turning ON the main switch MSW, charges the main capacitor MC in the flash light emitting circuit 303, lighting of the light emitting diode LED indicates the completion of charging of the main capacitor MC, and when the trigger switch TSW is turned ON being interlocked with the shutter blade, the electronic flash light emitting tube Xe emits light, so that the stroboscopic photographing is carried out.
In view of the foregoing problems, a first object of the present invention is to provide a single use camera with built-in electronic flash which finely exposes both of the main object and the background, in both cases of stroboscopic photographing and normal photographing using the single use camera with built-in electronic flash.
The other object of the present invention is to provide a single use camera with built-in electronic flash which can further reduce the size and cost of the single use camera.
In order to attain the other object of the present invention, the present inventor noticed that it is important to pay attention to a capacitor and a battery. In detail, the present inventor noticed the following: in the single use camera with built-in electronic flash, a main capacitor to be charged with the DC high voltage energy which is applied to a discharge tube to emit the flash light, and a battery as a power source of the electronic flash unit, specifically require a large space, and therefore, when capacity of the main capacitor is more reduced, capacity of the battery may also be the more reduced. Further, when the capacity of the main capacitor and that of the battery are more reduced, the cost is the more reduced.
Still another object of the present invention is to provide a single use camera with built-in electronic flash in which the life of the battery is prolonged by reducing current consumption to the utmost in the electronic flash circuit, thereby, the stroboscopic photographing can be carried out for a long period of time.
Yet another object of the present invention is to provide a single use camera with built-in electronic flash, provided with a flash circuit having the same function as that in the case where 2 switches are provided, while only one switch which is used for both of the main switch and the light emission stop switch, is provided.
Further object of the present invention is to provide a single use camera with built-in electronic flash in which the trigger voltage is adequate even when a light emitting diode is used.
Yet further object of the present invention is to provide a single use camera with built-in electronic flash in which an LED lighting circuit is independently provided electrically so that the lighting function of the light emitting diode does not interfere with the charging function for the flash light emission.
The above objects are attained by any of the following structures (1) to (6).
(1) A single use camera with built-in electronic flash characterized in that a roll film having the sensitivity not less than ISO 640 is previously loaded therein and the capacity of a main capacitor of a flash unit is not less than 15 xcexcF and not more than 80 xcexcF.
(2) A single use camera with built-in electronic flash includes a main body; a photographic film loaded previously in the main body; an electronic flash unit having an electronic flash light emitting section and an electronic flash circuit; and a photographic unit having a photographic lens and shutter, and the single use camera further satisfies the following conditional relationship:
6xe2x89xa6Axe2x89xa610, and A+1xe2x89xa6Bxe2x89xa6A+4,
where A: an exposure value converted into the film sensitivity of ISO 100 which is determined by an aperture value and shutter speed in the state of stroboscopic photographing, and the sensitivity of loaded film; and
B: an exposure value converted into the film sensitivity of ISO 100 which is determined by an aperture value and shutter speed in the state of normal photographing, and the sensitivity of loaded film.
(3) A single use camera with built-in electronic flash having a flash circuit comprising: an oscillating transformer to step up the source voltage to high voltage; a main capacitor which is connected to the oscillating transformer and to which the stepped up high voltage is applied; a trigger capacitor connected to one end of the main capacitor through a resistor; and a trigger coil to apply the high voltage onto a xenon tube by circulating electric charges accumulated in the trigger capacitor, the single use camera with built-in electronic flash characterized in that a flash circuit is provided, in which one end of a main switch, which is manually opened/closed, is connected to a portion between a secondary winding and a tertiary winding of the oscillating transformer, and is connected to one end of the trigger capacitor; and the other end of the main switch is connected to a base of the oscillating transistor to oscillate the oscillating transformer; and an emitter of the oscillating transistor is electrically grounded.
(4) A single use camera with built-in electronic flash having a flash circuit comprising: an oscillating transformer to step up the source voltage to high voltage; a main capacitor which is connected to the oscillating transformer and to which the stepped up high voltage is applied; a trigger capacitor connected to one end of the main capacitor through a resistor; and a trigger coil to apply the high voltage onto a xenon tube by circulating electric charges accumulated in the trigger capacitor, the single use camera with built-in electronic flash characterized in that a base of the oscillating transistor to oscillate the oscillating transformer is connected to a portion between the secondary winding and the tertiary winding of the oscillating transformer, and one end of the trigger capacitor; one end of the main switch which is manually opened/closed, is connected to the emitter of the oscillating transistor; and the other end of the main switch is electrically grounded.
(5) A single use camera in which a camera main body previously accommodating an unexposed roll film therein, is integrally provided with a flash unit; an oscillating transformer having a primary winding, a secondary winding and a tertiary winding, and a resistor to control a current in the step-up circuit are provided in a step-up circuit of a flash circuit; and a state holding type actuator is used for a flash switch actuator to operate a main switch in the flash circuit, the single use camera characterized in that the resistor in the step-up circuit is set to a value of 1 Kxcexa9 to 200 Kxcexa9.
(6) A single use camera in which a camera main body previously accommodating an unexposed roll of film therein, is integrally provided with a flash unit; and an oscillating transformer having a primary winding to n-th order winding for flash light emission, and a light emitting diode as an indicator lamp, are provided in a step-up circuit of a flash circuit, the single use camera characterized in that a winding for the light emitting diode is provided in the oscillating transformer separately from the primary winding to n-th order winding for the flash light emission, and the light emitting diode is connected to both ends of the winding for the light emitting diode, thereby, the light emitting diode lighting circuit is structured.